Multi-link piston-crank mechanism for internal combustion engine

Abstract

When the compression ratio of a variable compression ratio internal combustion engine ( 10 ) is set at a low compression ratio, a lubricating oil ejected from a lower link oil passage ( 25 ) is reflected by an upper link ( 11 ) at the piston top dead center, and supplied to a cylinder inside wall surface on the side on which a control link ( 15 ) is located in a view as viewed in the axial direction of the crank shaft. When the compression ratio of the variable compression ratio internal combustion engine ( 10 ) is set at a high compression ratio, the lubricating oil ejected from lower link oil passage ( 25 ) is reflected by upper link ( 11 ) at the piston top dead center, and supplied to the back side of the piston crown.

The invention claimed is: 
     
       1. A multi-link piston-crank mechanism for an internal combustion engine, comprising an upper link connected with a piston through a piston pin, a lower link attached rotatably to a crank pin of a crank shaft and connected swingably with the upper link through a first connecting pin, a control link including one end connected swingably with the lower link through a second connecting pin, and a control shaft which is attached rotatably to a cylinder block and which includes an eccentric shaft supporting the other end of the control link swingably, the first connecting pin being located on one side of a cylinder center axial line and the second connecting pin being located on the other side of the cylinder center axial line,
 wherein the lower link is formed with a lower link oil passage which communicates with a crank pin oil passage extending in a radial direction of the crank pin, at a predetermined swing posture of the lower link, and ejects a lubricating oil toward the upper link to cause the lubricating oil to be reflected by the upper link, and the upper link is arranged to reflect the lubricating oil ejected from the lower link oil passage and thereby to supply the lubricating oil to a cylinder inside wall surface on a side on which the control link is located as viewed in an axial direction of the crank shaft. 
 
     
     
       2. The multi-link piston-crank mechanism as claimed in  claim 1 , wherein the multi-link piston-crank mechanism is arranged to supply the lubricating oil reflected by the upper link, to the cylinder inside wall surface near a skirt of the piston at a time of piston top dead center. 
     
     
       3. The multi-link piston-crank mechanism as claimed in  claim 1 , wherein the multi-link piston-crank mechanism is adapted to control an eccentric shaft position of the control shaft in accordance with an engine operating condition and thereby to vary an engine compression ratio, and the multi-link piston-crank mechanism is arranged to supply the lubricating oil reflected by the upper link, to the cylinder inside wall surface near a skirt of the piston when the engine compression ratio is set at a low compression ratio. 
     
     
       4. The multi-link piston-crank mechanism as claimed in  claim 3 , wherein the multi-link piston-crank mechanism is arranged to supply the lubricating oil reflected by the upper link, to a back side of a crown of the piston when the engine compression ratio is set at a high compression ratio. 
     
     
       5. The multi-link piston-crank mechanism as claimed in  claim 1 , wherein the multi-link piston-crank mechanism is adapted to control an eccentric shaft position of the control shaft in accordance with an engine operating condition and thereby to vary an engine compression ratio, and
 the multi-link piston-crank mechanism is arranged to supply the lubricating oil reflected by the upper link, to the cylinder inside wall surface near a skirt of the piston at a time of piston top dead center when the engine compression ratio is set at a low compression ratio, and 
 to supply the lubricating oil reflected by the upper link, to a back side of a crown of the piston at the time of piston top dead center when the engine compression ratio is set at a high compression ratio. 
 
     
     
       6. The multi-link piston-crank mechanism as claimed in  claim 1 , wherein the first connecting pin is located on a first side of the cylinder center axial line; the second connecting pin is located on a second side of the cylinder center axial line opposite to the first side; the lower link oil passage of the lower link is opened to eject the lubricating oil in a predetermined first direction toward the upper link on the first side, away from a target region of the cylinder inside wall surface on the second side; and the upper link includes a portion to redirect the lubricating oil jetting out from the lower link oil passage toward the upper link and bumping against the portion of the upper link, from the first direction to a second direction toward the target region of the cylinder inside wall surface on the second side to supply the lubricating oil to the target region of the cylinder inside wall surface. 
     
     
       7. A multi-link piston-crank mechanism for an internal combustion engine, comprising
 upper link means for transmitting movement from a piston slidably received in a cylinder, by being connected with the piston through a piston pin; 
 lower link means, mounted rotatably on a crank pin of a crank shaft, for receiving movement from the upper link means by being connected swingably with the upper link means through first connecting means located on a first side of a predetermined imaginary center plane extending in parallel to an axis of the crank shaft and passing through the piston; 
 control link means including a first end connected swingably with the lower link means through second connecting means located on a second side of the center plane opposite to the first side, for constraining movement of the lower link means; 
 actuating means for supporting a second end of the control link means swingably; and 
 lubricating means for supplying a lubricating oil to a target region of a cylinder inside wall surface of the cylinder on the second side of the center plane, the lubricating means comprising, 
 ejecting means for ejecting the lubricating oil from the lower link means toward the first side, and 
 redirecting means, included in the upper link means, for receiving the lubricating oil ejected toward the first side by the ejecting means and redirecting a course of the lubricating oil toward the second side to supply the lubricating oil to the target region of the cylinder inside wall surface on the second side.